An adage in the business world is that a lost call is a lost opportunity. Many businesses, if not most, therefore provide their employees with voice mail so that if they do miss a call, the calling party is able to leave a message which the called party can then return. While the need is perhaps greatest for a business, many individuals also do not want to miss any telephone calls and therefore rely on answering machines or answering services to allow the calling party to leave a message.
A typical voice mail system includes a voice mail server for storing the voice messages. When an incoming call is not answered at a particular telephone, the voice mail server answers the call and presents the calling party with a prerecorded greeting, usually in the voice of the called party. After the greeting has been played, the voice mail server prompts the calling party to leave a message and records any message left by the calling party. The voice mail server activates an indicator at the called telephone, such as by flashing a message light, to notify the called party that a message has been stored. The called party thereafter calls the voice mail server and enters his or her extension and password in order to retrieve the stored message. The voice mail server then plays the message for the called party. The voice mail server may be located at the premises of the called party or may be remotely located, such as at a Service Control Node (SCN) within the Public Switched Telephone Network (PSTN).
Voice mail is not limited to wireline telephones but is also a service available to mobile radiotelephones. As with wireline telephones, a call to a mobile radiotelephone is answered by a voice mail server after a predetermined number of rings. The voice mail server plays a greeting to the calling party, prompts the party to leave a message, and then stores the message on behalf of the called party. The called party can thereafter call into the voice mail server and retrieve the message.
Because mobile radiotelephone are wireless devices, voice mail for mobile radiotelephones presents some difficulties not associated with wireline telephones. One of these challenges is notifying the called party that a message has been stored on its behalf. An Electronics Industries Association/Telecommunications Industry Association (EIA/TIA) Interim Standard (IS) 41C and EIA/TIA IS-136 addresses this problem by enabling a Message Waiting Indicator (MWI). In operation, when a message is stored for a mobile radiotelephone, the voice mail server sets a flag in a Home Location Register (HLR) for the mobile radiotelephone. When communications are later established with the mobile radiotelephone, the HLR sets an MWI indicator on the handset to notify the user that a message has been received. The MWI indicator, for instance, may consist of a message icon on an LCD display. The user then initiates a call to the voice mail server to listen to the message.
An example of a voice mail server for mobile radiotelephones having message waiting indication is described in U.S. Pat. No. 5,313,515 to Allen et al. The system includes an exchange and a voice messaging center connected to the exchange. The exchange connects a caller to a desired telephone and, if the call is not answered, diverts the call to the voice messaging center for recording a message from the caller. After the message has been stored, the voice message center transmits a message waiting flag for that telephone to the exchange. The exchange, in turn, transmits a message waiting signal to the telephone when it registers with a cell of the network or if the telephone initiates an outgoing call. To retrieve the stored message, the user then calls into the voice message center. The user may manually initiate the call by dialing or pressing one or more keys or, alternatively, the handset may automatically initiate the call to the voice messaging center.
One limitation of conventional voice mail for mobile radiotelephones is that the user may be notified of a message but is temporarily unable to retrieve the message. The user, for instance, may have turned off the mobile radiotelephone when a calling party attempts to place a call to the mobile radiotelephone. In such circumstances, the voice mail server will answer the call and record a message for the user. If the user later turns on the mobile radiotelephone, the MWI flag will be set in the mobile radiotelephone by the mobile radiotelephone network. The user, however, may not notice that the MWI indicator has been set until the user leaves the operating range of the network. The user would therefore have to wait until service becomes available with the mobile radiotelephone or until the user can reach a wireline telephone. This delay may be unacceptable, especially if the call was urgent and the calling party needed a prompt response from the user. Other situations, such as low battery, also occur preventing the user from retrieving his or her messages from the voice mail server.
Another problem endemic to mobile radiotelephones is that the call to the voice mail server from the mobile radiotelephone can be costly. To retrieve a message, a user must acquire a voice channel and call into the voice mail server. Upon reaching the voice mail server, the user typically enters a password and possibly his or her mailbox number. The voice mail server then plays the stored messages to the user and the user is presented with options as to actions that may be taken on the stored messages. The user, for instance, may erase the message, save the message, or forward the message. A significant amount of time can be consumed while the user calls into the voice mail server, listens to the messages, and performs additional actions on the messages. Because the user is charged by a cellular service provider based on the amount of air time consumed, the voice mail service for a user can become expensive due to the air time used in retrieving and otherwise managing his or her voice messages.